Complement activation on B lymphocytes opsonized with rituximab or ofatumumab produces substantial changes in membrane structure preceding cell lysis

DNA Nanostructure-Templated Antibody Complexes Provide Insights into the Geometric Requirements of Human Complement Cascade Activation

The classical complement pathway is activated by antigen-bound IgG antibodies. Monomeric IgG must oligomerize to activate complement via the hexameric C1q complex, and hexamerizing mutants of IgG appear as promising therapeutic candidates. However, structural data have shown that it is not necessary to bind all six C1q arms to initiate complement, revealing a symmetry mismatch between C1 and the hexameric IgG complex that has not been adequately explained. Here, we use DNA nanotechnology to produce specific nanostructures to template antigens and thereby spatially control IgG valency. These DNA-nanotemplated IgG complexes can activate complement on cell-mimetic lipid membranes, which enabled us to determine the effect of IgG valency on complement activation without the requirement to mutate antibodies. We investigated this using biophysical assays together with 3D cryo-electron tomography. Our data revealed the importance of interantigen distance on antibody-mediated complement activation, and that the cleavage of complement component C4 by the C1 complex is proportional to the number of ideally spaced antigens. Increased IgG valency also translated to better terminal pathway activation and membrane attack complex formation. Together, these data provide insights into how nanopatterning antigen-antibody complexes influence the activation of the C1 complex and suggest routes to modulate complement activation by antibody engineering. Furthermore, to our knowledge, this is the first time DNA nanotechnology has been used to study the activation of the complement system.

The Acquisition of Complement-Dependent Cytotoxicity by the Type II Anti-CD20 Therapeutic Antibody Obinutuzumab

Rituximab, a prototypic anti-CD20 mAb, and the third-generation anti-CD20 mAb obinutuzumab differ in their ability to activate the complement system. According to recent studies, this contrast stems from the architecture of the antigen-antibody complex formed by these two mAbs that facilitates (rituximab) or disables (obinutuzumab) further oligomerization, leading to engagement of the initial classical complement pathway component C1q. We examined whether a gain-of-function C2 variant that acts downstream of C1q and enforces the formation of complement convertase resistant to physiological decay can impact complement activation by obinutuzumab. Co-application of the C2 variant with obinutuzumab and human serum resulted in complement-dependent cytotoxicity equal to or higher than attainable for rituximab. This effect was observed either in serum or hirudin-anticoagulated whole blood. Long-term (24 h) overall cytotoxicity of obinutuzumab was improved in target cells of moderate sensitivity to complement but diminished in cells of low sensitivity. Our results demonstrate that the ability of complement activation of a given antibody is not ultimately determined at the stage of initial interactions with its target antigen but is modulable at later stages of the cascade and that the benefit of the acquisition of this new effector mechanism by obinutuzumab depends on the target cell characteristics.

The Development of Ofatumumab, a Fully Human Anti-CD20 Monoclonal Antibody for Practical Use in Relapsing Multiple Sclerosis Treatment

The importance of B cells in multiple sclerosis (MS) has been demonstrated through the advent of B-cell-depleting anti-CD20 antibody therapies. Ofatumumab is the first fully human anti-CD20 monoclonal antibody (mAb) developed and tested for subcutaneous (SC) self-administration at monthly doses of 20 mg, and has been approved in the US, UK, EU, and other regions and countries worldwide for the treatment of relapsing MS. The development goal of ofatumumab was to obtain a highly efficacious anti-CD20 therapy, with a safety and tolerability profile that allows for self-administration by MS patients at home and a positive benefit-risk balance for use in the broad relapsing MS population. This development goal was enabled by the unique binding site, higher affinity to B cells, and higher potency of ofatumumab compared to previous anti-CD20 mAbs; these properties of ofatumumab facilitate rapid B-cell depletion and maintenance with a low dose at a low injection volume (20 mg/0.4 ml). The high potency in turn enables the selective targeting of B cells that reside in the lymphatic system via subcutaneous (SC) administration. Through a comprehensive dose-finding program in two phase 2 studies (one intravenous and one SC) and model simulations, it was found that safety and tolerability can be further improved, and the risk of systemic injection-related reactions (IRRs) minimized, by avoiding doses ≥ 30 mg, and by reaching initial and rapid B-cell depletion via stepwise weekly administration of ofatumumab at Weeks 0, 1, and 2 (instead of a single high dose). Once near-complete B-cell depletion is reached, it can be maintained by monthly doses of 20 mg/0.4 ml. Indeed, in phase 3 trials (ASCLEPIOS I/II), rapid and sustained near-complete B-cell depletion (largely independent of body weight, race and other factors) was observed with this dosing regimen, which resulted in superior efficacy of ofatumumab versus teriflunomide on relapse rates, disability worsening, neuronal injury (serum neurofilament light chain), and imaging outcomes. Likely due to its fully human nature, ofatumumab has a low immunogenic risk profile-only 2 of 914 patients receiving ofatumumab in ASCLEPIOS I/II developed anti-drug antibodies-and this may also underlie the infrequent IRRs (20% with ofatumumab vs. 15% with the placebo injection in the teriflunomide arm) that were mostly (99.8%) mild to moderate in severity. The overall rates of infections and serious infections in patients treated with ofatumumab were similar to those in patients treated with teriflunomide (51.6% vs. 52.7% and 2.5% vs. 1.8%, respectively). The benefit-risk profile of ofatumumab was favorable compared to teriflunomide in the broad RMS population, and also in the predefined subgroups of both recently diagnosed and/or treatment-naïve patients, as well as previously disease-modifying therapy-treated patients. Interim data from the ongoing extension study (ALITHIOS) have shown that long-term treatment with ofatumumab up to 4 years is well-tolerated in RMS patients, with no new safety risks identified. In parallel to the phase 3 trials in which SC administration was carried out with a pre-filled syringe, an autoinjector pen for more convenient self-administration of the ofatumumab 20 mg dose was developed and is available for use in clinical practice.

Complement membrane attack complex is an immunometabolic regulator of NLRP3 activation and IL-18 secretion in human macrophages

The complement system is an ancient and critical part of innate immunity. Recent studies have highlighted novel roles of complement beyond lysis of invading pathogens with implications in regulating the innate immune response, as well as contributing to metabolic reprogramming of T-cells, synoviocytes as well as cells in the CNS. These findings hint that complement can be an immunometabolic regulator, but whether this is also the case for the terminal step of the complement pathway, the membrane attack complex (MAC) is not clear. In this study we focused on determining whether MAC is an immunometabolic regulator of the innate immune response in human monocyte-derived macrophages. Here, we uncover previously uncharacterized metabolic changes and mitochondrial dysfunction occurring downstream of MAC deposition. These alterations in glycolytic flux and mitochondrial morphology and function mediate NLRP3 inflammasome activation, pro-inflammatory cytokine release and gasdermin D formation. Together, these data elucidate a novel signalling cascade, with metabolic alterations at its center, in MAC-stimulated human macrophages that drives an inflammatory consequence in an immunologically relevant cell type.

Rituximab induces rapid blood repopulation by CLL cells mediated through their release from immune niches and complement exhaustion

The in vivo rituximab effects in B cell malignancies are only partially understood. Here we analyzed in a large chronic lymphocytic leukemia (CLL) cohort (n = 80) the inter-patient variability in CLL cell count reduction within the first 24 h of rituximab administration in vivo, and a phenomenon of blood repopulation by malignant cells after anti-CD20 antibody therapy. Larger CLL cell elimination after rituximab infusion was associated with lower pre-therapy CLL cell counts, higher CD20 levels, and the non-exhausted capacity of complement-dependent cytotoxicity (CDC). The absolute amount of cell-surface CD20 molecules (CD20 density x CLL lymphocytosis) was a predictor for complement exhaustion during therapy. We also describe that a highly variable decrease in CLL cell counts at 5 h (88 %-2%) following rituximab infusion is accompanied in most patients by peripheral blood repopulation with CLL cells at 24 h, and in ∼20 % of patients, this resulted in CLL counts higher than before therapy. We provide evidence that CLL cells recrudescence is linked with i) CDC exhaustion, which leads to the formation of an insufficient amount of membrane attack complexes, likely resulting in temporary retention of surviving rituximab-opsonized cells by the mononuclear-phagocyte system (followed by their release back to blood), and ii) CLL cells regression from immune niches (CXCR4^dimCD5^bright intraclonal subpopulation). Patients with major peripheral blood CLL cell repopulation exhibited a longer time-to-progression after chemoimmunotherapy compared to patients with lower or no repopulation, suggesting chemotherapy vulnerability of CLL cells that repopulate the blood.

A Milestone in Multiple Sclerosis Therapy: Monoclonal Antibodies Against CD20-Yet Progress Continues

Multiple sclerosis (MS), which is a chronic inflammatory disease of the central nervous system, still represents one of the most common causes of persisting disability with an early disease onset. Growing evidence suggests B cells to play a crucial role in its pathogenesis and progression. Over the last decades, monoclonal antibodies (mabs) against the surface protein CD20 have been intensively studied as a B cell targeting therapy in relapsing MS (RMS) as well as primary progressive MS (PPMS). Pivotal studies on anti-CD20 therapy in RMS showed remarkable clinical and radiological effects, especially on acute inflammation and relapse biology. These results paved the way for further research on the implication of B cells in the pathogenesis of MS. Besides controlling relapse development in RMS, ocrelizumab (OCR) also showed clinical benefits in patients with PPMS and became the first approved drug for this disease course. In this review, we provide an overview of the current anti-CD20 mabs used or tested for the treatment of MS-namely rituximab (RTX), OCR, ofatumumab (OFA), and ublituximab (UB). Besides their effectiveness, we also discuss possible limitations and safety concerns especially in regard to long-term treatment, both for this class of drugs overall as well as for each anti-CD20 mab individually. Additionally, we elucidate to what extent anti-CD20 therapy may alter the function of other immune cells, both directly or indirectly. Finally, we cover the current knowledge on repopulation of CD20+ cells after cessation of anti-CD20 treatment and discuss future aspirations towards alternative, further developed B cell silencing therapies.

Comparison of the Efficacy and Safety of Anti-CD20 B Cells Depleting Drugs in Multiple Sclerosis

Rituximab, ocrelizumab, ofatumumab and ublituximab are disease modifying therapies (DMT) currently used in the treatment of multiple sclerosis (MS) or are in advanced stages of clinical trials. These monoclonal antibodies deplete B cells by targeting the cell surface protein CD20. This review highlights the similarities and major differences between the four agents. We summarize data from various clinical trials of each of these therapeutics and discuss their efficacy and safety. Additional considerations regarding the route of administration and cost are presented. Among the four therapeutics, only ocrelizumab is approved for primary progressive (PP) MS. Infusion/injection related reactions (IRRs) are the most common adverse events associated with all four therapeutics. In phase III trials of ocrelizumab and ofatumumab, the incidence of IRRs was lower with ofatumumab. Ofatumumab is unique among the four therapeutics due to its availability as a subcutaneous injection (SQ). Although SQ administration may be appealing for some patients it may raise concerns regarding medication compliance among physicians. Phase II trials studying ublituximab for the treatment of RMS yielded promising results. Phase III trials are currently comparing the efficacy of ublituximab to teriflunomide.

Complement System: a Neglected Pathway in Immunotherapy

Approved for the treatment of autoimmune diseases, hematological malignancies, and solid cancers, several monoclonal antibodies (mAb) make use of complement in their mechanism of action. Such an assessment is based on comprehensive investigations that used mouse models, in vitro studies, and analyses from patients at initiation (basal level to highlight deficiencies) and after treatment initiation (mAb impact on complement), which have further provided key insights into the importance of the complement activation and/or complement deficiencies in mAb activity. Accordingly, new approaches can now be developed with the final objective of increasing the clinical efficacy of mAb. These improvements include (i) the concurrent administration of fresh frozen plasma during mAb therapy; (ii) mAb modifications such as immunoglobulin G subclass switching, Fc mutation, or IgG hexamerization to improve the fixation and activation of C1q; (iii) optimization of the target recognition to induce a higher complement-dependent cytotoxicity (CDC) and/or complement-dependant cellular cytotoxicity (CDCC); and (iv) the control of soluble and cellular complement inhibitors.

How Do mAbs Make Use of Complement to Kill Cancer Cells? The Role of Ca2

We examined the kinetics and mechanisms by which monoclonal antibodies (mAbs) utilize complement to rapidly kill targeted cancer cells. Based on results from flow cytometry, confocal microscopy and high-resolution digital imaging experiments, the general patterns which have emerged reveal cytotoxic activities mediated by substantial and lethal Ca2+ fluxes. The Ca2+ fluxes are common to the reported pathways that have been utilized by other toxins in killing nucleated cells. These reactions terminate in very high levels of cell killing, and based on these considerations, we suggest additional strategies to further enhance mAb-based targeting of cancer with complement.

Mechanisms of Resistance to Monoclonal Antibodies (mAbs) in Lymphoid Malignancies

PURPOSE OF REVIEW

Passive immunotherapy with therapeutic monoclonal antibodies (mAbs) has revolutionized the treatment of cancer, especially hematological malignancies over the last 20 years. While use of mAbs has improved outcomes, development of resistance is inevitable in most cases, hindering the long-term survival of cancer patients. This review focuses on the available data on mechanisms of resistance to rituximab and includes some additional information for other mAbs currently in use in hematological malignancies.

RECENT FINDINGS

Mechanisms of resistance have been identified that target all described mechanisms of mAb activity including altered antigen expression or binding, impaired complement-mediated cytotoxicity (CMC) or antibody-dependent cellular cytotoxicity (ADCC), altered intracellular signaling effects, and inhibition of direct induction of cell death. Numerous approaches to circumvent identified mechanisms of resistance continue to be investigated, but a thorough understanding of which resistance mechanisms are most clinically relevant is still elusive. In recent years, a deeper understanding of the tumor microenvironment and targeting the apoptotic pathway has led to promising breakthroughs. Resistance may be driven by unique patient-, disease-, and antibody-related factors. Understanding the mechanisms of resistance to mAbs will guide the development of strategies to overcome resistance and re-sensitize cancer cells to these biological agents.

Immunotherapy in Patients with Recurrent and Metastatic Squamous Cell Carcinoma of the Head and Neck

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is the most common malignant cancer occurring in the head and neck area, approximately 90% of the cases. Even in the cases of primary radical treatment (surgical, concomitant chemoradiotherapy or radiotherapy alone), subsequent local recurrence or distant metastases are often observed. In patients with recurrent disease who are unable to receive radical treatment, the results of palliative chemotherapy are not satisfactory. In this review, we summarized the standard treatment options, current development of new drugs and future perspectives in the treatment of patients with recurrent locally advanced and/or metastatic HNSCC.

METHODS

PubMed databases with words 'head and neck cancer treatment', 'immunotherapy in head and neck cancer treatment' were searched and yielded 186512 and 2249 papers respectively. We selected the most cited articles and reports presenting new immunotherapy agents and drug combinations in HNSCC.

RESULTS

Recently, two new agents been approved in the treatment of recurrent locally advanced and/or metastatic HNSCC. These are immune-checkpoint inhibitors targeting PD1 (nivolumab and pembrolizumab) which are the most active drugs in the second line treatment of advanced HNSCC. Still, the first line 'golden standard' is the chemotherapy regimen (cisplatin, 5-fluorouracyl) combined with cetuximab. Many phase 3 studies are currently ongoing, evaluating the efficacy of combinational treatment-anti-CTLA4 with anti-PD1 or anti-PDL1. Very encouraging results have been shown in early phase studies evaluating the combination of immunecheckpoint inhibitors with tumor microenvironment immunosuppressive inhibitors.

CONCLUSION

Despite the huge progress in the systemic treatment of patients with recurrent locally advanced and/or metastatic HNSCC, the disease at this stage remains incurable. Undoubtedly, further research in the field of biomarkers for effective immunotherapy is needed in order to select a group of patients whose will benefit from this therapy, as the treatment is still ineffective in most patients.

Resistance to complement activation, cell membrane hypersialylation and relapses in chronic lymphocytic leukemia patients treated with rituximab and chemotherapy

The anti-CD20-specific monoclonal antibody rituximab (RTX), in combination with chemotherapy, is commonly used for primary treatment in chronic lymphocytic leukemia (CLL). However, relapses remain important and activation of the complement pathway is one of the mechanisms by which RTX generates the destruction of B cells directly by complement-dependent cytotoxicity (CDC), or indirectly by antibody-dependent cellular phagocytosis. In this study, the RTX capacity to induce CDC was established in 69 untreated CLL patients, this cohort including 34 patients tested before the initiation of RTX-chemotherapy. In vitro CDC-resistance to RTX predicts lower response rates to RTX-chemotherapy and shorter treatment free survival. Furthermore, the predictive value of CDC-resistance was independent from the clinical, cytogenetic and FcγR3A V158F polymorphism status. In contrast, CLL cell resistance to CDC predominates in IGHV unmutated patients and was related to an important α2-6 sialyl transferase activity, which in turn increases cell surface α2-6 hypersialylation. Suspected factors associated with resistance to CDC (CD20, CD55, CD59, factor H, GM1, and sphingomyelin) were not differentially expressed or recruited between the two CLL groups. Altogether, results provide evidence that testing RTX capacity to induce CDC in vitro represents an independent predictive factor of therapeutic effects of RTX, and that α2-6 hypersialylation in CLL cells controls RTX response through the control of the complement pathway. At a time when CLL therapy is moving towards chemo-free treatments, further experiments are required to determine whether performing an initial in vitro assay to appreciate CLL CDC resistance might be useful to select patients.

A Chimeric Antibody against ACKR3/CXCR7 in Combination with TMZ Activates Immune Responses and Extends Survival in Mouse GBM Models

Glioblastoma (GBM) is the least treatable type of brain tumor, afflicting over 15,000 people per year in the United States. Patients have a median survival of 16 months, and over 95% die within 5 years. The chemokine receptor ACKR3 is selectively expressed on both GBM cells and tumor-associated blood vessels. High tumor expression of ACKR3 correlates with poor prognosis and potential treatment resistance, making it an attractive therapeutic target. We engineered a single chain FV-human FC-immunoglobulin G1 (IgG₁) antibody, X7Ab, to target ACKR3 in human and mouse GBM cells. We used hydrodynamic gene transfer to overexpress the antibody, with efficacy in vivo. X7Ab kills GBM tumor cells and ACKR3-expressing vascular endothelial cells by engaging the cytotoxic activity of natural killer (NK) cells and complement and the phagocytic activity of macrophages. Combining X7Ab with TMZ allows the TMZ dosage to be lowered, without compromising therapeutic efficacy. Mice treated with X7Ab and in combination with TMZ showed significant tumor reduction by MRI and longer survival overall. Brain-tumor-infiltrating leukocyte analysis revealed that X7Ab enhances the activation of M1 macrophages to support anti-tumor immune response in vivo. Targeting ACKR3 with immunotherapeutic monoclonal antibodies (mAbs) in combination with standard of care therapies may prove effective in treating GBM.

Pharmacokinetic Considerations for Antibody-Drug Conjugates against Cancer

Antibody-drug conjugates (ADCs) are ushering in the next era of targeted therapy against cancer. An ADC for cancer therapy consists of a potent cytotoxic payload that is attached to a tumour-targeted antibody by a chemical linker, usually with an average drug-to-antibody ratio (DAR) of 3.5-4. The theory is to deliver potent cytotoxic payloads directly to tumour cells while sparing healthy cells. However, practical application has proven to be more difficult. At present there are only two ADCs approved for clinical use. Nevertheless, in the last decade there has been an explosion of options for ADC engineering to optimize target selection, Fc receptor interactions, linker, payload and more. Evaluation of these strategies requires an understanding of the mechanistic underpinnings of ADC pharmacokinetics. Development of ADCs for use in cancer further requires an understanding of tumour properties and kinetics within the tumour environment, and how the presence of cancer as a disease will impact distribution and elimination. Key pharmacokinetic considerations for the successful design and clinical application of ADCs in oncology are explored in this review, with a focus on the mechanistic determinants of distribution and elimination.

Anti-CD20 monoclonal antibodies in chronic lymphocytic leukemia: from uncertainties to promises

Over the last two decades, anti-CD20 monoclonal antibody (mAb) therapy has improved patient outcome in B-cell malignancies, and confirmed CD20 as an important target in chronic lymphocytic leukemia (CLL). Until recently, the gold standard was based on the utilization of rituximab combined with chemotherapy (fludarabine and cyclophosphamide), but patients often relapse. Next, with our better understanding of mAb engineering, anti-CD20 mAb therapy has evolved with the development of new mAb permitting significant clinical responses by improving pharmacokinetics, safety, activity and immunogenicity. Last but not least, the development of key tumoral tyrosine kinase inhibitors and their association with anti-CD20 mAb is a work in progress with promising results.

IgG Fc domains that bind C1q but not effector Fcγ receptors delineate the importance of complement-mediated effector functions

Engineered crystallizable fragment (Fc) regions of antibody domains, which assume a unique and unprecedented asymmetric structure within the homodimeric Fc polypeptide, enable completely selective binding to the complement component C1q and activation of complement via the classical pathway without any concomitant engagement of the Fcγ receptor (FcγR). We used the engineered Fc domains to demonstrate in vitro and in mouse models that for therapeutic antibodies, complement-dependent cell-mediated cytotoxicity (CDCC) and complement-dependent cell-mediated phagocytosis (CDCP) by immunological effector molecules mediated the clearance of target cells with kinetics and efficacy comparable to those of the FcγR-dependent effector functions that are much better studied, while they circumvented certain adverse reactions associated with FcγR engagement. Collectively, our data highlight the importance of CDCC and CDCP in monoclonal-antibody function and provide an experimental approach for delineating the effect of complement-dependent effector-cell engagement in various therapeutic settings.

Associations of ofatumumab exposure and treatment outcomes in patients with untreated CLL receiving chemoimmunotherapy

Relationships between patient characteristics, ofatumumab pharmacokinetics, and treatment outcomes were investigated in this phase 2 trial of ofatumumab plus fludarabine and cyclophosphamide (FC) in untreated chronic lymphocytic leukemia. Patients were randomized 1:1 to receive 500 or 1000 mg ofatumumab (Cycle 1; 300 mg) plus FC every 4 weeks for six cycles. Median C_max and C_trough values were similar at Cycle 1 regardless of the ultimate clinical outcome. At later doses, these values were higher for patients with complete response (CR) than for other patients. Higher C_max and C_trough values at Cycles 3 and 6 were significantly associated with an increased likelihood of CR, whereas ofatumumab pharmacokinetics were not associated with an objective response (OR) on the basis of univariate analyses. Multivariate analyses indicated that baseline patient/disease factors were predominantly associated with CR (17p status) or OR (bulky lymphadenopathy, gender, and serum thymidine kinase), rather than ofatumumab pharmacokinetics.

TRIAL REGISTRATION

www.clinicaltrials.gov (NCT00410163).

The missing link: does tunnelling nanotube-based supercellularity provide a new understanding of chronic and lifestyle diseases?

Tunnelling nanotubes (TNTs) are increasingly recognized as central players in a multitude of cellular mechanisms and diseases. Although their existence and functions in animal organisms are still elusive, emerging evidence suggests that they are involved in developmental processes, tissue regeneration, viral infections or pathogen transfer, stem cell differentiation, immune responses as well as initiation and progression of neurodegenerative disorders and cancer (see Sisakhtnezhad & Khosravi 2015 Eur. J. Cell Biol. 94, 429-443. (doi:10.1016/j.ejcb.2015.06.010)). A broader field of vision, including their striking functional and structural resemblance with nanotube-mediated phenomena found throughout the phylogenetic tree, from plants down to bacteria, points to a universal, conserved and tightly regulated mechanism of cellular assemblies. Based on our initial definition of TNTs as open-ended channels mediating membrane continuity between connected cells (Rustom et al. 2004 Science 303, 1007-1010. (doi:10.1126/science.1093133)), it is suggested that animal tissues represent supercellular assemblies that-besides opening discrete communication pathways-balance diverse stress factors caused by pathological changes or fluctuating physiological and environmental conditions, such as oxidative stress or nutrient shortage. By combining current knowledge about nanotube formation, intercellular transfer and communication phenomena as well as associated molecular pathways, a model evolves, predicting that the linkage between reactive oxygen species, TNT-based supercellularity and the intercellular shuttling of materials will have significant impact on diverse body functions, such as cell survival, redox/metabolic homeostasis and mitochondrial heteroplasmy. It implies that TNTs are intimately linked to the physiological and pathological state of animal cells and represent a central joint element of diverse diseases, such as neurodegenerative disorders, diabetes or cancer.

Immunotherapeutic approaches for the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma

With the introduction of the anti-CD20 monoclonal antibody rituximab, B-cell non-Hodgkin lymphoma was the first malignancy successfully treated with an immunotherapeutic agent. Since then, numerous advances have expanded the repertoire of immunotherapeutic agents available for the treatment of a variety of malignancies, including many lymphoma subtypes. These include the introduction of monoclonal antibodies targeting a variety of cell surface proteins, including the successful targeting of immunoregulatory checkpoint receptors present on T-cells or tumour cells. Additionally, cellular immunotherapeutic approaches utilize T- or Natural Killer-cells generated with chimeric antigen receptors against cell surface proteins or Epstein-Barr virus-associated latent membrane proteins. The following review describes the current state of immunotherapy for non-Hodgkin lymphoma including a summary of currently available data and promising agents currently in clinical development with future promise in the treatment of childhood, adolescent and young adult non-Hodgkin lymphoma.

Cytotoxic mechanisms of immunotherapy: Harnessing complement in the action of anti-tumor monoclonal antibodies

Several mAbs that have been approved for the treatment of cancer make use of complement-dependent cytotoxicity (CDC) to eliminate tumor cells. Comprehensive investigations, based on in vitro studies, mouse models and analyses of patient blood samples after mAb treatment have provided key insights into the details of individual steps in the CDC reaction. Based on the lessons learned from these studies, new and innovative approaches are now being developed to increase the clinical efficacy of next generation mAbs with respect to CDC. These improvements include engineering changes in the mAbs to enhance their ability to activate complement. In addition, mAb dosing paradigms are being developed that take into account the capacity as well as the limitations of the complement system to eliminate a substantial burden of mAb-opsonized cells. Over the next few years it is likely these approaches will lead to mAbs that are far more effective in the treatment of cancer.

New developments in the management of chronic lymphocytic leukemia: role of ofatumumab

Ofatumumab is one of the three anti-CD20 monoclonal antibodies currently available for the treatment of chronic lymphocytic leukemia (CLL). The US Food and Drug Administration (FDA) approved the use of ofatumumab in patients with CLL refractory to fludarabine and alemtuzumab in 2009, and the European Medicines Agency (EMA) granted approval for the same indication in 2010. Subsequent positive results of ofatumumab in combination with chlorambucil in treatment-naïve patients led the FDA in April 2014 to approve the use of this combination for first-line treatment of patients with CLL for whom fludarabine-based therapy is considered inappropriate. Later that year, the EMA approved the use of ofatumumab in combination with chlorambucil or bendamustine for the same indication. Ofatumumab has also shown potential as maintenance therapy for patients with relapsed CLL; an application to broaden the label for ofatumumab as maintenance therapy was submitted earlier this year to the EMA and FDA. Finally, ofatumumab has shown promising activity in combination with ibrutinib or idelalisib in relapsed/refractory CLL patients; combinations of ofatumumab with B-cell-receptor pathway inhibitors could represent another potential use of this antibody in the near future.

Safety and efficacy of different lenalidomide starting doses in patients with relapsed or refractory chronic lymphocytic leukemia: results of an international multicenter double-blinded randomized phase II trial

The objective of this study was to evaluate the safety and efficacy of different lenalidomide starting doses in patients with relapsed/refractory chronic lymphocytic leukemia (CLL). CLL patients were randomized to receive lenalidomide at initial doses of 5, 10, or 15 mg/d (N = 103). Doses were escalated by 5 mg every 28-d up to a maximum of 25 mg/d; dose reductions in up to 5 mg decrements were permitted. The most common grade ≥3 adverse events (AEs) were neutropenia and thrombocytopenia. Ten patients died during therapy (four deaths considered as related to lenalidomide); 12 patients experienced second primary malignancies. The most common cause for treatment discontinuation was AEs. Overall response rates were similar across arms. Progression-free survival and overall survival rates were longer in patients who escalated treatment (to 15 or 20 mg/d) versus those who did not. Lower starting doses allowed subsequent dose escalation of lenalidomide while maintaining an acceptable tolerability profile in patients with relapsed/refractory CLL.

Targeted therapy for chronic lymphocytic leukemia: current status and future directions

The majority of patients with chronic lymphocytic leukemia (CLL) respond to chemo-immunotherapy. However, long-term remission remains elusive and the majority of patients will die of complications related to CLL. In this review we discuss the recent developments in targeted therapy for CLL. Targeted therapy has evolved beyond the cell surface targeting of CD20 with rituximab. Our review focuses on the evolution of antibody therapy in CLL, strategies to target effector T cells to the tumor, inhibition of the B-cell receptor signaling pathway, and finally targeting the mediators of apoptosis. With our improved understanding of the biology of CLL, the evolution of targeted therapy has resulted in significant clinical responses in patients who are refractory to traditional treatment options and holds the potential for a future where we can manage this disease without chemotherapy.

Mesothelin-specific cell-based vaccine generates antigen-specific immunity and potent antitumor effects by combining with IL-12 immunomodulator

Ovarian cancer is a gynecologic malignancy with a high mortality rate. In the present study, we developed a novel cell-based vaccine, Meso-VAX, to generate mesothelin antigen-specific immune responses and immunotherapy against ovarian cancer. Mesothelin, a secreted protein anchored at the cell membrane, has recently been identified as a potential new tumor antigen for ovarian cancer. In this study, mice vaccinated with Meso-VAX and adeno-associated virus (AAV)-IL-12 exhibited dramatic increases in the number of mesothelin-specific CD4(+) helper and CD8(+) cytotoxic T-cell precursors, higher titers of anti-mesothelin Abs and in vitro tumor killing activity, and all of these mice were tumor-free after 60 days of tumor challenge. In addition, a significant reduction in peritoneal tumors and longer survival were noted in the mice vaccinated with Meso-VAX combined with AAV-IL-12. CD4(+) helper and CD8(+) cytotoxic T lymphocytes were essential for the antitumor effect generated by Meso-VAX combined with AAV-IL-12. The post-vaccination sera of the mice vaccinated with Meso-VAX and AAV-IL-12 also showed mesothelin-specific complement-dependent cell-mediated cytotoxicity. Our results suggest that a Meso-VAX cell-based vaccine combined with AAV-IL-12 can generate antigen-specific immunological responses and antitumor effects on ovarian cancer.

Ofatumumab Exhibits Enhanced In Vitro and In Vivo Activity Compared to Rituximab in Preclinical Models of Mantle Cell Lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is a mature B-cell lymphoma considered to be incurable with current treatments, including first-line rituximab in combination with multiagent chemotherapy and for those eligible, high-dose chemotherapy and stem cell support or rituximab maintenance. On the other hand, achieving a complete remission by high-sensitive flow cytometry is associated with prolonged duration of remission, stressing the need to develop and/or incorporate novel agents into the management of MCL. To this end, we examined the activity of ofatumumab, an anti-CD20 monoclonal antibody with distinct binding and immunologic properties compared to rituximab, in MCL preclinical models.

EXPERIMENTAL DESIGN

MCL cells were labeled with (51)Cr before incubation with rituximab or ofatumumab (10 μg/mL) plus human serum or effector cells. (51)Cr-release was measured and the percentage of lysis was calculated. Surface CD20, CD55, and CD59 were measured by Imagestream analysis. SCID mice inoculated subcutaneously with Z138 cells were assigned to control versus four doses of ofatumumab or rituximab (10 mg/kg/dose).

RESULTS

Ofatumumab exhibited enhanced in vitro complement-dependent cytotoxicity activity compared with rituximab in MCL cell lines, despite a high degree of in vitro resistance to rituximab associated with low CD20 levels and/or high expression of complement inhibitory proteins. Ofatumumab also delayed tumor progression and prolonged survival in a murine model of MCL.

CONCLUSIONS

Our results demonstrate that ofatumumab is more effective than rituximab in MCL preclinical models, including in the presence of rituximab resistance, and support the clinical investigation of ofatumumab in combination with standard systemic chemotherapy in MCL (NCT01527149).

Chlorambucil plus ofatumumab versus chlorambucil alone in previously untreated patients with chronic lymphocytic leukaemia (COMPLEMENT 1): a randomised, multicentre, open-label phase 3 trial

BACKGROUND

Treatment for patients with chronic lymphocytic leukaemia who are elderly or who have comorbidities is challenging because fludarabine-based chemoimmunotherapies are mostly not suitable. Chlorambucil remains the standard of care in many countries. We aimed to investigate whether the addition of ofatumumab to chlorambucil could lead to better clinical outcomes than does treatment with chlorambucil alone, while also being tolerable for patients who have few treatment options.

METHODS

We carried out a randomised, open-label, phase 3 trial for treatment-naive patients with chronic lymphocytic leukaemia in 109 centres in 16 countries. We included patients who had active disease needing treatment, but in whom fludarabine-based treatment was not possible. We randomly assigned patients (1:1) to receive oral chlorambucil (10 mg/m(2)) on days 1-7 of a 28 day treatment course or to receive chlorambucil by this schedule plus intravenous ofatumumab (cycle 1: 300 mg on day 1 and 1000 mg on day 8; subsequent cycles: 1000 mg on day 1) for three to 12 cycles. Assignment was done with a randomisation list that was computer generated at GlaxoSmithKline, and was stratified, in a block size of two, by age, disease stage, and performance status. The primary endpoint was progression-free survival in the intention-to-treat population and assessment was done by an independent review committee that was masked to group assignment. The study is registered with ClinicalTrials.gov, number NCT00748189.

FINDINGS

We enrolled 447 patients, median age 69 years (range 35-92). Between Dec 22, 2008, and May 26, 2011, we randomly assigned 221 patients to chlorambucil plus ofatumumab and 226 patients to chlorambucil alone. Median progression-free survival was 22·4 months (95% CI 19·0-25·2) in the group assigned to chlorambucil plus ofatumumab compared with 13·1 months (10·6-13·8) in the group assigned to chlorambucil only (hazard ratio 0·57, 95% CI 0·45-0·72; p<0·0001). Grade 3 or greater adverse events were more common in the chlorambucil plus ofatumumab group (109 [50%] patients; vs 98 [43%] given chlorambucil alone), with neutropenia being the most common event (56 [26%] vs 32 [14%]). Grade 3 or greater infections had similar frequency in both groups. Grade 3 or greater infusion-related adverse events were reported in 22 (10%) patients given chlorambucil plus ofatumumab. Five (2%) patients died during treatment in each group.

INTERPRETATION

Addition of ofatumumab to chlorambucil led to clinically important improvements with a manageable side-effect profile in treatment-naive patients with chronic lymphocytic leukaemia who were elderly or had comorbidities. Chlorambucil plus ofatumumab is therefore an important treatment option for these patients who cannot tolerate more intensive therapy.

FUNDING

GlaxoSmithKline, Genmab A/S.

Ofatumumab added to dexamethasone in patients with relapsed or refractory chronic lymphocytic leukemia: Results from a phase II study

The treatment of relapsed/refractory chronic lymphocytic leukemia (CLL) remains a challenging clinical issue. An important treatment option is the use of high-dose corticosteroids. The purpose of this clinical trial was to determine the efficacy and toxicity of an ofatumumab-dexamethasone (O-Dex) combination in relapsed or refractory CLL. The trial was an open-label, multicenter, nonrandomized, Phase II study. The O-Dex regimen consisted of intravenous ofatumumab (Cycle 1: 300 mg on day 1, 2,000 mg on days 8, 15, and 22; Cycles 2-6: 1,000 mg on days 1, 8, 15, and 22) and oral dexamethasone (40 mg on days 1-4 and 15-18; Cycles 1-6). The O-Dex regimen was given until best response, or a maximum of six cycles. Thirty-three patients (pts) were recruited. Twenty-four (73%) pts completed at least three cycles of therapy. The remaining nine pts were prematurely discontinued owing to Grade 3/4 infections (seven pts), disease progression (one pt), or uncontrollable diabetes mellitus (one pt). Overall response rates/complete remissions (ORR/CR) were achieved in 22/5 pts (67/15%). The median progression-free survival (PFS) was 10 months. In pts with p53 defects (n = 8), ORR/CR were achieved in 5/2 pts (63/25%) with a median PFS of 10.5 months. The median overall survival (OS) was 34 months. The Grades 3-5 infectious toxicity in 33% of pts represented the most frequent side effect during the treatment period. In conclusion, the O-Dex regimen shows a relatively high ORR and CR with promising findings for PFS and OS. The study was registered at www.clinicaltrials.gov (NCT01310101).

Ofatumumab in combination with glucocorticoids for primary therapy of chronic graft-versus-host disease: phase I trial results

Standard primary therapy for chronic graft-versus-host disease (GVHD) is incompletely effective. Based on biologic insights implicating pathogenic B cells, we conducted a phase I trial examining the combination of standard (1 mg/kg/day prednisone) glucocorticoid therapy with ofatumumab, a humanized anti-CD20 monoclonal antibody, for primary chronic GVHD therapy. Patients ages ≥ 18 with National Institutes of Health Consensus moderate-to-severe chronic GVHD newly requiring 1 mg/kg/day prednisone were treated at 3 escalating dose levels (300 mg, 700 mg, and 1000 mg) of i.v. ofatumumab on days 1 and 14 of initial glucocorticoid therapy. Dose-limiting toxicity (DLT) was defined by grade 4 infusion reactions, related grade 4 constitutional symptoms, related grade ≥ 3 organ toxicities, or grade 4 neutropenia lasting > 14 days. A total of 12 patients (median age 54; range, 25 to 72) were treated (dose level 1: n = 3; level 2: n = 3; level 3: n = 6). At enrollment, overall chronic GVHD was moderate (n = 7) or severe (n = 5), with diverse organ involvement (skin: n = 8; mouth: n = 8; eye: n = 8; lung: n = 4; gastrointestinal: n = 3; liver: n = 5; genital: n = 2; joint/fascia: n = 5). Infusion of ofatumumab was well tolerated, and no DLT was observed. From the total number of adverse events (n = 29), possibly related adverse events (n = 4) included grade 1 fatigue, grade 1 transaminitis, and 2 infusion reactions (grades 2 and 3). Infectious complications were expected, and there were no cases of hepatitis B reactivation or progressive multifocal leukoencephalopathy. Ofatumumab in combination with prednisone is safe and a phase II examination of efficacy is ongoing.

Promising therapies for the treatment of chronic lymphocytic leukemia

INTRODUCTION

The combination schedule of fludarabine, cyclophosphamide and rituximab is the gold standard of therapy for younger, physically fit chronic lymphocytic leukemia (CLL) patients; it allows achieving high and durable complete response rates. Although treatment outcome has considerably improved with chemo-immunotherapy, most patients eventually relapse and CLL is still incurable. Thus, newer and more rationally developed drugs are needed to improve CLL therapy, particularly in cases of relapsed/refractory disease.

AREAS COVERED

The authors review preclinical and clinical data regarding newer CLL agents, currently undergoing examination, such as: signal transduction and cyclin-dependent kinase inhibitors, immunomodulatory agents, B-cell lymphoma 2 inhibitors, next generation mAbs, heat shock protein 90 and histone deacetylase inhibitors, and chimeric antigen receptor T-cell therapy.

EXPERT OPINION

Newer compounds with different mechanisms of action, such as B-cell receptor signal transduction inhibitors, lenalidomide, next generation mAbs and several pro-apoptotic molecules, have shown efficacy in relapsed or refractory CLL patients. Several studies are under way to investigate the efficacy of combinations of these novel drugs. Hopefully, the combined use of these molecules in risk-adapted treatment strategies will change the therapeutic approach in the near future and will pave the way for a long-term control of CLL.

Complement in therapy and disease: Regulating the complement system with antibody-based therapeutics

Complement is recognized as a key player in a wide range of normal as well as disease-related immune, developmental and homeostatic processes. Knowledge of complement components, structures, interactions, and cross-talk with other biological systems continues to grow and this leads to novel treatments for cancer, infectious, autoimmune- or age-related diseases as well as for preventing transplantation rejection. Antibodies are superbly suited to be developed into therapeutics with appropriate complement stimulatory or inhibitory activity. Here we review the design, development and future of antibody-based drugs that enhance or dampen the complement system.

High plasma fibrinogen is correlated with poor response to trastuzumab treatment in HER2 positive breast cancer

Some of HER-2 positive breast cancer patients failed to trastuzumab treatment. Recent reports have indicated the correlation between plasma coagulation parameters and clinical characteristics in breast cancer. The aim of this study was to analyze the role of coagulation parameters in trastuzumab treated patients. Coagulation parameters from trastuzumab treated breast cancer patients were retrospectively studied from 2006 to 2010. The correlation between routine coagulation levels and clinical characteristics were analyzed, including prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen (Fib) and D-dimer (DD). The Kaplan-Meier analysis and Cox regression hazard model were applied to assess their effect on prognosis. Totally 102 hospitalized breast cancer patients who received trastuzumab were collected and followed-up. All patients were HER-2 positive advanced breast cancer, with a median age of 45 years old. Extended PT, APTT, and TT were found in trastuzumab treatment non-effective group, as well as increased Fib and DD. But significant increase was only found in Fib. High Fib status (Fib > 2.88 g/L) was correlated with clinical characteristics, such as pathological grade, and reversely correlated with PTEN expression. More importantly, poor disease-free survival (DFS) and overall survival (OS) to trastuzumab treatment were found in high Fib breast cancer patients. This retrospective study suggests high Fib status was correlated with poor treatment response to trastuzumab. Our findings indicated that Fib > 2.88 should alert physicians to consider a pretreatment for reducing Fib levels before trastuzumab treatment in HER-2 positive breast cancer patients.

Ofatumumab in poor-prognosis chronic lymphocytic leukemia: a phase IV, non-interventional, observational study from the European Research Initiative on Chronic Lymphocytic Leukemia

We report the largest retrospective, phase IV non-interventional, observational study of ofatumumab therapy in heavily pre-treated patients with poor-prognosis chronic lymphocytic leukemia. Total number of patients was 103; median age was 65 years (range 39-85). Median number of prior lines of therapy was 4 (range 1-13), including, in most cases, rituximab-, fludarabine- and alemtuzumab-based regimens; 13 patients had been allografted. Of 113 adverse events, 28 (29%) were considered to be directly related to ofatumumab. Grade 3-4 toxicities included neutropenia (10%), thrombocytopenia (5%), anemia (3%), pneumonia (17%), and fever (3%). Two heavily pre-treated patients developed progressive multifocal leukoencephalopathy. On an intention-to-treat analysis, the overall response rate was 22% (3 complete response, 1 incomplete complete response). Median progression-free and overall survival times were 5 and 11 months, respectively. This study confirms in a daily-life setting the feasibility and acceptable toxicity of ofatumumab treatment in advanced chronic lymphocytic leukemia. The complete response rate, however, was low. Therefore, treatment with ofatumumab should be moved to earlier phases of the disease. Ideally, this should be done in combination with other agents, as recently approved for ofatumumab plus chlorambucil as front-line treatment for patients unfit for fludarabine. This study is registered at clinicaltrials.gov identifier:01453062.

Ofatumumab: a novel, fully human anti-CD20 monoclonal antibody for the treatment of chronic lymphocytic leukemia

Ofatumumab is a fully human, IgG anti-CD20 monoclonal antibody codeveloped by GlaxoSmithKline (Brentford, UK) and Genmab (Copenhagen, Denmark). In preclinical studies, ofatumumab exhibited more potent in vitro activity than rituximab against B-cell malignancies and prolonged survival in in vivo animal models compared with rituximab. Ofatumumab is clinically well tolerated with initial infusion reactions being the predominant associated toxicity. Ofatumumab has demonstrated efficacy in relapsed/refractory chronic lymphocytic leukemia (CLL) and has received regulatory approval in both Europe and the USA for treatment of fludarabine and alemtuzumab refractory disease. Single-agent ofatumumab has resulted in overall response rates of 42-51% in relapsed/refractory CLL and up to 80% when combined with chemotherapy. In de novo CLL, overall response rates of 77-78% have been achieved.

New treatment options for chronic lymphocytic leukemia

INTRODUCTION

Chemoimmunotherapy is the gold standard of therapy for patients with advanced chronic lymphocytic leukemia (CLL), resulting in high and durable complete response rates. However, all patients eventually relapse and CLL remains incurable. Newer and more rationally developed compounds are needed to improve CLL therapy, particularly in cases of refractory disease.

AREAS COVERED

Following a literature search on PubMed using 'chronic', 'lymphocytic', 'treatment' and 'therapy' as keywords, results obtained with novel agents were critically analyzed. Abstracts presented during 2013 at ASH, EHA, ICML, IWCLL and ASCO meetings were also included in the search.

EXPERT OPINION

New monoclonal antibodies, lenalidomide, B-cell receptor-signal transduction inhibitors and pro-apoptotic molecules have shown efficacy in patients with relapsed or refractory disease. Hopefully, the combined use of these molecules in risk-adapted treatment strategies will improve the outcome of patients with CLL and pave the way for their long-term control.

Tunneling nanotubes: Diversity in morphology and structure

Tunneling nanotubes (TNTs) are recently discovered thin membranous tubes that interconnect cells. During the last decade, research has shown TNTs to be diverse in morphology and composition, varying between and within cell systems. In addition, the discovery of TNT-like extracellular protrusions, as well as observations of TNTs in vivo, has further enriched our knowledge on the diversity of TNT-like structures. Considering the complex molecular mechanisms underlying the formation of TNTs, as well as their different functions in intercellular communication, it is important to decipher how heterogeneity of TNTs is established, and to address what roles the compositional elements have in the execution of various functions. Here, we review the current knowledge on the morphological and structural diversity of TNTs, and address the relation between the formation, the structure, and the function of TNTs.

The role of complement in tumor growth

Complement is a central part of the immune system that has developed as a first defense against non-self cells. Neoplastic transformation is accompanied by an increased capacity of the malignant cells to activate complement. In fact, clinical data demonstrate complement activation in cancer patients. On the basis of the use of protective mechanisms by malignant cells, complement activation has traditionally been considered part of the body's immunosurveillance against cancer. Inhibitory mechanisms of complement activation allow cancer cells to escape from complement-mediated elimination and hamper the clinical efficacy of monoclonal antibody-based cancer immunotherapies. To overcome this limitation, many strategies have been developed with the goal of improving complement-mediated effector mechanisms. However, significant work in recent years has identified new and surprising roles for complement activation within the tumor microenvironment. Recent reports suggest that complement elements can promote tumor growth in the context of chronic inflammation. This chapter reviews the data describing the role of complement activation in cancer immunity, which offers insights that may aid the development of more effective therapeutic approaches to control cancer.

Activation of complement by monoclonal antibodies that target cell-associated β₂-microglobulin: implications for cancer immunotherapy

β₂-Microglobulin (β2M), the light chain of the class I major histocompatibilty complex (MHC-I), is a promising tumor target for monoclonal antibodies (mAbs) in cancer immunotherapy. Several reports indicate that chelation of cell-associated β2M by specific mouse mAbs promotes tumor cell destruction by inducing apoptosis or other cytotoxic signaling pathways. Human mAbs employed in cancer therapy are usually IgG1, which mediates cell-killing by effector mechanisms including complement dependent cytotoxicity (CDC). The analogous mouse IgG2a and IgG2b isotypes are similarly effective in activating complement. Therefore, we examined the complement-activating properties of anti-β2M mouse mAbs 1B749 (IgG2a) and HB28 (IgG2b) when either mAb was bound to tumor cell lines or normal cells; we compared these β2M-specific mAbs with mouse mAb W6/32 (IgG2a), specific for human leukocyte antigens in the MHC-I heavy chain. All three mAbs bind to most human cell lines and normal cells in approximately equal amounts, consistent with a 1:1 stoichiometry for the HLA heavy chain in association with β2M. The three mAbs promote rapid C3b deposition and substantial CDC of human cell lines, and mAbs 1B749 and W6/32 have robust cytotoxic activity on reaction with normal mononuclear cells and platelets. Curiously, mAb HB28 induces modest C3b deposition and little CDC of normal cells, and its weaker complement-fixing activity was confirmed by ELISA. Based on these findings, we suggest that human IgG mAbs that target β2M for cancer immunotherapy be selected or engineered so as not to activate complement, thus eliminating the potential adverse effects of complement-mediated lysis of normal cells.

The role of complement in mAb-based therapies of cancer

The ability of complement to promote lysis of antibody-opsonized cells is well-established. Virtually all of the molecular details of this reaction have been elucidated and numerous points of regulation have also been delineated. Use of this information, along with the techniques that were first applied in the fundamental studies of complement, has allowed for investigations of the role of complement in mAb-based immunotherapies of cancer. These studies, which have often combined in vitro investigations with parallel correlative clinical measurements, have revealed that several FDA-approved mAbs make use of complement as an effector function in promoting opsonization and killing of targeted malignant cells. We describe the key methods used in this work, and discuss how the results of these studies provide rational approaches for making more effective use of complement in mAb-based cancer immunotherapy.

Ofatumumab in combination with ICE or DHAP chemotherapy in relapsed or refractory intermediate grade B-cell lymphoma

Standard treatment of transplant-eligible patients with relapsed diffuse large B-cell lymphoma (DLBCL) consists of rituximab and platinum-based chemotherapy, either ifosfamide, carboplatin, and etoposide (ICE) or dexamethasone, cytarabine, and cisplatin (DHAP), with autologous transplant consolidation for those with chemosensitive disease. Nonetheless, outcomes are suboptimal for patients failing rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). We performed a multi-center phase II trial investigating the safety and efficacy of ofatumumab, a monoclonal antibody against CD20, combined with ICE or DHAP second-line therapy in patients with relapsed or refractory DLBCL, grade 3b follicular lymphoma, or transformed follicular lymphoma. Sixty-one patients were treated with either ofatumumab-ICE (35) or ofatumumab-DHAP (26). The overall response rate (ORR) was 61%, and the complete response (CR) rate was 37%. In patients with 2 or 3 adverse risk factors according to the second-line, age-adjusted, international prognostic index, the ORR was 59% and CR 31%, and in patients with early-relapsing or primary refractory disease, the ORR was 55% and CR 30%. Toxicity was largely hematologic, and stem cell mobilization was successful in 43 of 45 patients. Substitution of ofatumumab for rituximab in standard second-line regimens following failure of R-CHOP is a promising approach. This trial was registered at www.clinicaltrials.gov as NCT00823719.

The use of monoclonal antibodies in the treatment of autoimmune complications of chronic lymphocytic leukemia

Autoimmune cytopenias are a frequent complication in CLL, occurring in approximately 5-10% of the patients. The most common manifestation is autoimmune haemolytic anaemia, followed by immune thrombocytopenia and only rarely pure red blood cell aplasia or autoimmune granulocytopenia. Initial treatment is as for the idiopathic autoimmune cytopenias, with most patients responding to conventional corticosteroid therapy. Patients, who do not respond to conventional therapy after 4-6 weeks, should be considered for alternative immunosuppression, monoclonal antibody therapy or splenectomy. While randomized trials demonstrating the benefit of rituximab in CLL-related autoimmune diseases are still lacking, there are considerable data in the literature that provide evidence for its effectiveness. The monoclonal antibody alemtuzumab also displays considerable activity against both the malignant disease and the autoimmune complication in patients with CLL, although at the expense of greater toxicity. A number of new monoclonal antibodies, such as ofatumumab, GA-101, lumiliximab, TRU-016, epratuzumab, and galiximab, are currently investigated in CLL and their activity in CLL-related autoimmune cytopenias should be evaluated in future studies.

Emerging monoclonal antibodies and related agents for the treatment of chronic lymphocytic leukemia

Monoclonal antibodies (mAbs) – rituximab, ofatumumab and alemtuzumab – have been approved for use in the therapy of chronic lymphocytic leukemia (CLL). Recently, a new generation of anti-CD20 mAbs has become available for preclinical studies and clinical trials. These antibodies were engineered to have augmented antitumor activity by increasing complement-dependent cytotoxicity, antibody-dependent cellular cytotoxicity and Fc-binding affinity for the low-affinity variants of the Fcγ receptor IIIa. The most promising mAb directed against CD20 is obinutuzumab (GA-101). mAbs directed against CD22, CD37 and CD40 have also shown some activity in CLL. In addition, small modular immunopharmaceuticals – TRU-015 (anti-CD20) and TRU-016 (anti-CD37) – that retain Fc-mediated effector functions have been developed and investigated in preclinical studies and clinical trials. Antibody–drug conjugates and recombinant immunotoxins are also being evaluated in lymphoid malignancies. Further studies will elucidate the role of these agents in the treatment of CLL.